In recent years, an optical recording medium of a high-density recording in which information of a large volume can be recorded is demanded. For example, to meet the demand, the standard ver.1.1 of a Blu-ray Disc (registered trademark; hereinbelow, BD) has been specified and a high-definition image can be recorded and stored into the optical recording medium. Assuming that a normal reproducing speed of the high-definition is a one-time speed (1×), according to the standard ver.1.1 of the BD, the disc has already coped with the recording of up to a 2-times speed (2×).
However, a user demands a higher-speed for recording. At a speed near 10000 rpm which is considered to be a limit of a rotational speed of the disc, the disc has to cope with a 4-times speed (4×) in a CLV (Constant Linear Velocity) mode. Further, in the future, it is necessary to cope with the recording at a speed over a 10-times speed (10×) in a CAV (Constant Angular Velocity) mode. Therefore, it is necessary that the optical recording medium has sufficient recording characteristics even in such a high-speed recording.
On the other hand, as a BD-R (BD-Rewitable) media corresponding to the recording of up to the 2-times speed (2×), a media having an oxide film made of an oxide film of germanium (Ge) and a metal film which is provided adjacently to the oxide film and is made of titanium (Ti) is available on market (for example, refer to JP-A-2006-281751). Although such a write-once type optical recording medium is constructed by a 3-layered film or a 4-layered film, the medium has a wide power margin and high durability.